SPIRE Spectroscopy of Early Type Galaxies

Abstract

We present SPIRE spectroscopy for 9 early-type galaxies (ETGs) representing the most CO-rich and far-infrared (FIR) bright galaxies of the volume-limited Atlas3D sample. Our data include detections of mid to high J CO transitions (J=4-3 to J=13-12) and the [CI] (1-0) and (2-1) emission lines. CO spectral line energy distributions (SLEDs) for our ETGs indicate low gas excitation, barring NGC 1266. We use the [CI] emission lines to determine the excitation temperature of the neutral gas, as well as estimate the mass of molecular hydrogen. The masses agree well with masses derived from CO, making this technique very promising for high redshift galaxies. We do not find a trend between the [NII] 205 flux and the infrared luminosity, but we do find that the [NII] 205/CO(6-5) line ratio is correlated with the 60/100 $\mu$m Infrared Astronomical Satellite (IRAS) colors. Thus the [NII] 205/CO(6-5) ratio can be used to infer a dust temperature, and hence the intensity of the interstellar radiation field (ISRF). Photodissociation region (PDR) models show that use of [CI] and CO lines in addition to the typical [CII], [OI], and FIR fluxes drive the model solutions to higher densities and lower values of G${}_0$. In short, the SPIRE lines indicate that the atomic and molecular gas in the CO-rich ETGs have similar properties to other galaxies. As might be expected from their low levels of star formation activity, the ETGs have rather low excitation CO SLEDs, low temperatures inferred from the [CI] lines, and modestly lower [CI]/CO ratios.

References in corpus (12)

• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• Star formation relations and CO SLEDs across the J-ladder and redshift
• Structure and Kinematics of Molecular Disks in Fast-Rotator Early-Type Galaxies
• A Far-Infrared Spectroscopic Survey of Intermediate Redshift (Ultra) Luminous Infrared Galaxies
• A Survey of the Molecular ISM Properties of Nearby Galaxies using the Herschel FTS
• Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795
• A Herschel Survey of the [N II] 205 micron Line in Local Luminous Infrared Galaxies --- The [N II] 205 micron Emission as a Star Formation Rate Indicator
• Measuring Star-formation Rate and Far-Infrared Color in High-redshift Galaxies Using the CO (7-6) and [NII] 205 micron Lines
• Star Formation in Nearby Early-Type Galaxies: The Radio Continuum Perspective
• Systematic characterisation of the Herschel SPIRE Fourier Transform Spectrometer
• NGC 1266: Characterization of the Nuclear Molecular Gas in an Unusual SB0 Galaxy

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• Dust, CO and [CI]: Cross-calibration of molecular gas mass tracers in metal-rich galaxies across cosmic time
• Ionized Carbon in Galaxies: The [C II] 158 $\mu$m Line as a Total Molecular Gas Mass Tracer Revisited
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